The WADA (West Africa Data Base on Antiretroviral Therapy) Collaboration is a unique collaboration among cohorts in West Africa with a mission to conduct hypothesis-driven epidemiological research on the prognosis and outcomes of HIV-1 and HIV-2-infected people, including adults, pregnant mothers, and children in care and generally on treatment, as well as HIV-exposed children. Our five-year research plan will focus on scientific questions requiring a large sample size of patients that the contributing cohorts cannot answer individually and which do not overlap with existing projects. During the five years of the next leDEA round, the overall aims of WADA are:1)to measure the effectiveness of combination antiretroviral treatment (ART) in West Africa in the long term, and to assess factors that influence outcomes;2) to increase the capacity for delivering ART durably in West Africa by increasing the capacity for monitoring clinical outcomes at the individual and population levels in adults and children;3) to document the morbidity burden in HIV- infected individuals in care in HIV programs throughout West Africa. To date, the pooled database assembled by the WADA Collaboration in the current leDEA cycle includes 33,815 HIV-infected adults and 3,533 HIV- infected children who initiated ART in 26 clinics. The next round will involve 27 HIV centers (adults: 16, pediatrics: 11) in nine countries (Benin, Burkina Faso, Cote d'lvoire, Ghana, Guinea Bissau, Mali, Nigeria, Senegal, Togo). Among them, two new countries (Guinea Bissau and Togo) and five HIV clinics (three adult clinics and two pediatric clinics) are new collaborating centers. WADA is jointly coordinated by the WADA Coordinating Center at the Bordeaux School of Public Health (ISPED) in Bordeaux University, France (Prof. Francois Dabis) with a WADA Regional Office hosted by PAC-CI, a research-oriented non-governmental organization situated in Abidjan, Cote d'lvoire. This research team has a long-lasting experience in observational HIV research including large-scale prospective cohorts in West Africa and will continue and expand the ongoing leDEA-funded cycle. Data will be collected from affiliated cohorts every year according to standardized procedures. Capacity building in participating centers will include funding for local human resources, training on data quality, on-site technical support and annual meetings to reinforce the technical and scientific network. The priority research agenda will address the following topics: retention in care, natural history of HIV-2 and HIV-1/HIV-2 infections, cancer, malaria, hepatitis B, pregnancy outcomes, pharmacovigilance, adolescent and pediatric access and efficiency of care. RELEVANCE: Clinical and operational research assessing the efficiency of HIV care programs require reliable information systems and capacity building for sustaining this activity in the long term. The WADA collaboration has already implemented a network of HIV care centers and will reinforce its commitment to study morbidities including cancer, malaria, hepatitis B and adverse drug reactions. The HIV-2 cohort will be strengthened with the organization of a blood bank Children will be enrolled from the time of HIV exposure.